Laying khaki Campbell questions

I apologize for so many questions, but I am new to raising poultry so here goes. I have a hen and Drake pair khaki Campbell's that have been breeding for around a month now and this evening when I put them up I found 6 eggs in a nest. They are housed with 8 Rhode island reds and 2 Bourbon red turkeys. So here are my questions: how many eggs will my hen lay in one nest? How long can the eggs sit before they go bad? How do I know if they are fertile? How often will the hen sit on the eggs? What should I do if she is not sitting on them? We are raising the ducks for eggs to eat and hatch to raise babies for meat. We live in northern CA and the temperatures right now are between the upper 90's to 105. Any information is greatly appreciated!

Thank you so much for your reply! The info is very helpful. She has been averaging close to an egg a day. We decided to leave 5 in the nest and will be candling them in a few days. I haven't seen her sit on the nest unless she is doing so at night, but the days and nights have been very warm here. A few of our chickens just started laying as well so we are very excited!